Ad-hoc networking is becoming all the rage. We are somehow to believe that a collection of unorganized mobile nodes will be able to perpetuate a data packet irrespective of how an ad-hoc network is organized and maintained. It is well understood that a computer network needs to be managed in order to effectively use available resources when a data packet needs to be conveyed from a first node to a second node. Now, almost magically, ad-hoc networking purports to eliminate the need for high-level network management altogether.
When a data packet arrives at a stationary routing unit (e.g. a networking switch or router), the data packet is propagated according to a pre-established routing table. Included in a traditional routing unit is circuitry that uses the contents of the routing table to select one or more communications channels that will be used to propagate the data packet toward its final destination. In order to do this well, the routing table is built on pre-existing knowledge of a networks structure. For example, a first router will typically be connected to other routers, each of which is geographically disparate from the first router. The quality of a connection between the first router and the remaining routers is typically understood. Even when the quality of a connection varies over time, this time-varying connection can be reflected in the routing table by periodic updates to the contents of the routing table. As such, as the structure or quality of the connections between routers varies, so can the routing tables that the routers use to propagate a data packet.
As such, when a packet does arrive at a router, a portion of the destination address is used to select a particular entry in the router table. The selected entry is then used to direct the data packet to a particular communications channel. For example, when selected by a portion of the destination address, an entry in the routing table can cause the router to direct the data packet to a communications channel that connects a first router in Cleveland to a second router in Minneapolis. And, as the conditions of available channels changes over time, the same entry in the routing table can be modified in order to direct the data packet from Cleveland to St. Paul rather than to Minneapolis. What is important to note is that the communications channels are typically fixed from point-to-point and will only vary in the amount of data that each can carry over a particular time-varying quality profile. Even with all of this regularity, management of a data network is a complex and daunting task. So critical is the management of a network that many, many people devote their careers to the art of network management.
An ad-hoc network, on the other hand, is essentially impossible to manage because of the transient nature of individual connections between nodes. Just when a data packet can be directed to a particular neighbor node, the connection between a first node and its neighbor can be completely lost. Ad-hoc networking has simply not been able to solve this problem. That is why ad-hoc networking relies on the notion of discovering a neighbor node. Once a neighbor node is discovered, a data packet is blindly directed to the newly discovered neighbor node.
One of the problems with ad-hoc networking is that each node typically only has one communications channel that can be used to convey a data packet. There simply are not enough resources to intelligently route a data packet from a first mobile node to a newly discovered neighbor, especially when there are a plurality of mobile nodes within the communication range of the communication channel servicing the first mobile node.
In any type of networking structure, be it ad-hoc or fixed networks, there is even a more troublesome issue. Consider the situation where a data packet is propogated through any particular device in the network. For example, a data packet can be propagated through a fixed network by a switch, a router and various other network components. Up until now, it has always been assumed that the carrying costs for a connection are basically nil. That is because a data packet is routed through a fixed network is done so at no cost to the actual user. Generally, some large communications company has already made a fixed-capital investment by purchasing switches, routers and the cabling needed to string to whole network together. This type of large company is typically called a network operator. A network operator recoups its investment by charging for connections to the network (e.g. $19.95 per month). Of course, there are other contractual arrangements between the network operator and its customers that provide sufficient motivation for continued operation and expansion of the network by the network operator.
Ad-hoc networking changes the entire financial incentive strategy that has fueled continued expansion and upgrade of communications networks. In the situation where a slurry of ad-hoc nodes is to propagate a data packet, fixed networks will become more lightly loaded because of these additional routing resources (i.e. ad-hoc mobile networking nodes). At first blush, this appears to be a good thing because all of these additional resources will provide yet more bandwidth for today's communication driven society.
The problem with this simplistic view of the world it that there is simply no financial incentive for an ah-hoc network to participate in a data connection. Even more complex of an issue is the impact these mobile ad-hoc nodes will have on fixed installation networking systems and the financial models upon which network operators rely. If network traffic starts to use ad-hoc based connections, existing networking companies may not be able to demand higher connectivity prices from their customers. This, in turn, can have a devastating result for the networking infrastructure as a whole because network operators may not have the financial incentive to continue expansion and upgrade of their core communications competency.